A microbiologist's view of commissioning operating theatres

Microbial air monitoring in operating theatres: experience at the University Hospital of Parma

BACKGROUND

Microbial air monitoring in operating theatres has been a subject of interest and debate. No generally accepted sampling methods and threshold values are available.

AIM

To assess microbial air contamination in empty and working conventionally ventilated operating theatres over a three-year period at the University Hospital of Parma, Italy.

METHODS

Air sampling was performed in 29 operating theatres. Both active and passive sampling methods were used to assess bacterial and fungal contamination.

FINDINGS

In empty theatres, median bacterial values of 12 colony-forming units (cfu)/m(3) [interquartile range (IQR) 4-32] and 1 index of microbial air contamination (IMA) (IQR 0-3) were recorded. In working theatres, these values increased significantly (P < 0.001) to 80 cfu/m(3) (IQR 42-176) and 7 IMA (IQR 4-13). Maximum recorded values were 166 cfu/m(3) and 8 IMA for empty theatres, and 798 cfu/m(3) and 42 IMA for working theatres. Combining active and passive samplings, fungi were isolated in 39.13% of samples collected in empty theatres and 56.95% of samples collected in working theatres. Over the three-year study period, bacterial contamination decreased in both empty and working theatres, and the percentage of samples devoid of fungi increased. In working theatres, a significant correlation was found between the bacterial contamination values assessed using passive and active sampling methods (P < 0.001).

CONCLUSION

Microbiological monitoring is a useful tool for assessment of the contamination of operating theatres in order to improve air quality.

Assessing the efficacy of photocatalytic oxidation on bacterial contamination in a clinical setting – a randomised controlled trial

Airborne contamination has been shown to be a significant source of wound contamination in orthopaedic surgery. This is the first reported study looking at the efficacy of ActivTek 300, a portable UV/TiO2-based air purifier unit to reduce airborne contamination in a clinical setting. In this randomised study the investigator was blinded as to whether the unit had been on or off for the previous seven days.

Air contamination was measured weekly using a validated technique in ward treatment rooms using a Mini Air Sampler (MAS-100) and agar plates, over a period of 12 weeks. The agar plates were then incubated for 24 hours and the results were expressed as number of colony forming units per plate (cfu). The biomedical scientist who manually counted the number of cfus was blinded as to whether the unit was on or off. Measurements were duplicated to improve the accuracy of the study, and in addition to this an identical experiment was set up in a second treatment room on a separate randomisation schedule. Analysis of the data demonstrated median colony count was significantly lower with the unit on (Median = 43 interquartile range (IQR) 30 to 83) than when it was off (median = 95 IQR 44 to 143) ( p < 0.01). This represents a 55% mean reduction in the colony count. This study suggests that the portable UV/TiO2-based air purifier unit is efficacious in reducing airborne contamination in the clinical environment and may have a promising role in reducing overall infection rates in surgical patients.

Impact of Protective Footwear on Floor and Air Contamination of Intensive Care Units

BACKGROUND

Use of protective footwear before entering the intensive care units is enforced with the assumption that it lowers the incidence of bacterial floor colonization. The present study was carried out to find the efficacy of protective footwear on bacterial floor colonization.

METHODS

The study was carried out in the intensive care unit of a tertiary care hospital. The study was divided into two phases of two weeks each, phase I with and phase II without use of protective footwear. Samples were taken at six different sites namely footwear exchange area; visitors /staff route; partitioned patient cubicle; central monitoring area; open patient cubicle and scrub up areas. Floor samples were taken at 0600, 1100, 1700 and 2200 hours and air samples at 0600 and 1700 hours. Bacteria were identified and colony forming units (cfu) measured from floor and colony forming units/metre(3) (cfu/m3) from air sample cultures.

RESULT

A total of 9521 bacterial colony forming units were isolated from 192 samples in phase I from the floor samples and 9971cfu from 192 samples in phase II. From 96 air samples in each phase, a mean of 262 cfu/m(3) in phase I and 220cfu/m(3) in phase II were isolated. The difference between the two phases was statistically not significant (p value > 0.05 for both).

CONCLUSION

Floor and air colony counts showed no significant difference in the two phases with and without protective footwear. Protective footwear had no significant impact on bacterial contamination of floors.

Factors involved in the aerosol transmission of infection and control of ventilation in healthcare premises

The epidemics of severe acute respiratory syndrome (SARS) in 2003 highlighted both short- and long-range transmission routes, i.e. between infected patients and healthcare workers, and between distant locations. With other infections such as tuberculosis, measles and chickenpox, the concept of aerosol transmission is so well accepted that isolation of such patients is the norm. With current concerns about a possible approaching influenza pandemic, the control of transmission via infectious air has become more important. Therefore, the aim of this review is to describe the factors involved in: (1) the generation of an infectious aerosol, (2) the transmission of infectious droplets or droplet nuclei from this aerosol, and (3) the potential for inhalation of such droplets or droplet nuclei by a susceptible host. On this basis, recommendations are made to improve the control of aerosol-transmitted infections in hospitals as well as in the design and construction of future isolation facilities.

Do anaesthetists need to wear surgical masks in the operating theatre? A literature review with evidence-based recommendations

Many operating theatre staff believe that the surgical face mask protects the healthcare worker from potentially hazardous biological infections. A questionnaire-based survey, undertaken by Leyland' in 1993 to assess attitudes to the use of masks, showed that 20% of surgeons discarded surgical masks for endoscopic work. Less than 50% did not wear the mask as recommended by the Medical Research Council. Equal numbers of surgeons wore the mask in the belief they were protecting themselves and the patient, with 20% of these admitting that tradition was the only reason for wearing them. Policies relating to the wearing of surgical masks by operating theatre staff are varied. This indicates some confusion about the role of the surgical mask in modern surgical and anaesthetic practice. This review was undertaken to collate current evidence and make recommendations based on this evidence.

Survey of operating theatres in Great Britain and Ireland

A survey of operating theatres in Great Britain and Ireland by postal questionnaire was undertaken to determine the number of non-ventilated theatres in use, the number of designated theatres for specialist surgery and how and when bacterial sampling is conducted. Replies were received from 147 centres covering 438 operating theatre suites. Eighty-seven (59%) centres contained three or fewer suites and only 32% did not have a designated theatre for any specialist surgery. One hundred and seventy-three (40%) theatre suites were built over 20 years ago and 28 non-ventilated theatres were identified, mainly used for minor surgery (e.g. removal of 'lumps'). Four percent of plenum and 9% of ultraclean theatres are never monitored bacteriologically and settle plates are used in 72 (49%) centres. This survey suggests there is some confusion over the indications for bacteriological monitoring and what constitutes acceptable standards. The use of non-ventilated theatres, except for the most minor of procedures, is of some concern and should be phased out.

Bacteriological studies of open versus closed contrast medium delivery systems in angiography

The aim of this study was to evaluate the safety of the 'open' method of contrast medium delivery in the angiographic theatre, in which contrast medium is decanted into open galley pots on sterile trolleys. The air bacterial load within the angiographic theatre was sampled before and during angiographic procedures. The relationship of staff and patient activity to bacterial load was assessed. Samples of Iopromide (Ultravist 370; Schering Pty Ltd, Sydney, NSW, Australia) decanted into galley pots were taken for bacterial culture at the end of seven patient procedures. Air bacterial loads were comparable with operating theatre levels and were heaviest during staff activity. Three of seven samples taken at the end of angiographic procedures from air-exposed galley pots yielded contaminants, but the number of bacteria was below that required to produce septicaemia under normal conditions. These results suggest that the open system of contrast medium delivery can be safely used, providing that bacterial checks of room contamination are performed and personnel entry into the theatre is strictly limited.

Multiple doses of contrast medium from a single container: bacteriological studies

Preparations of Iopromide (Ultravist 370; Schering Pty Ltd, Sydney, NSW, Australia), brain/heart infusion broth (BHI; positive growth control) and distilled water (negative control) were inoculated with 10(3) to 10(4) Pseudomonas aeruginosa, Escherichia coli or Staphylococcus aureus cells and incubated at 37 degrees C. Slow decreases (up to one log) were observed in each organism's count in Iopromide and distilled water at room temperature and in S. aureus and E. coli in Iopromide and distilled water at 35 degrees C until 6-8 h, when counts stabilized. BHI cultures showed logarithmic increases. P. aeruginosa counts increased (half log over 8 h) in Ultravist at 37 degrees C. Radiology laboratories were shown to have similar airborne bacterial loads to operating theatres. Samples from repeatedly entered Iopromide bottles showed no contamination. Multiple intravenous doses from a single bottle of non-ionic contrast medium can safely be used as a cost-saving measure provided scrupulous attention is paid to aseptic preparation. Unused decanted contrast medium should be discarded after 4 h.

The effect of surgical theatre head-gear on air bacterial counts

The wearing of disposable head-gear in operating theatres is currently recommended for scrubbed and non-scrubbed staff. However, there is little evidence of its effectiveness as an infection control measure in casual or non-scrubbed theatre staff. The effect of head-gear on bacterial air counts was studied, using six volunteers, in a sealed room, with and without ventilation. Using a Casella slit sampler and a SAS Air Sampler, air counts ranged from 0.08 to greater than 2.9 colony forming units (cfu) m-3. The wearing of head-gear was not associated with a reduction in air counts but counts were lower with ventilation. We recommend that non-scrubbed staff no longer wear head-gear as effective ventilation probably counteracts any possible increased bacterial shedding. Scrubbed staff should continue to wear disposable head-gear because of their proximity to the operative field.